Signaling and transmission circuits



am 11, 1929. H LADNER 1,716,447

S IGNALING AND" TRKNSMISS ION CIRCUITS Filed Dec. 15, 192'? Supervisory W Ili l lilll Relay HIIIiHII INVENTORS E lad/W A TTORNEY Patented June 11, 1929.

HENRY LADNER, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, CORPORATION OF NEW vYORK.

SIGNALING AND TRANSMISSION CIRCUITS.

Application filed December 15, 1927. Serial No. 240,183..

This invention relates to transmissionlines and more particularly to improvements in the talking and signaling paths comprising such lines.

The invention is particularly applicable to the type of transmission line in which the talking and signaling, or supervisory, paths are distinct and separate from each other. In the arrangements of the invention a pushpull transmitter is utilized and the source of battery supply, is connected to the line'in such a manner that the currents therefrom traverse both sides of the line in parallel with ground return over the central electrode of the push-pull transmitter. Under such conditions the talking path will comprise a complete metallic circuit, while the supervisory paths will be parallel grounded circuits over each side of the line. The receiver relay has a double winding so arranged that the supervisory currents will not affect the receiver relay.

The arrangements of the above type of system present many distinct advantages over the types of full metallic circuits heretofore used. By connecting the battery supply so that the currents therefrom will traverse both sides of the line in parallel with ground return will cause the supervisory or signaling paths to possess only one fourth as much resistance as that of former metallic loops. For this reason, from a supervisory or signaling standpoint, loop lengths may be made four times as great as in former arrangements. The transmission efficiency is also increased because of a lower battery supply loss in the transmitter, due to the decreased resistance of the battery supply path. The double winding receiver relay will result in a material decrease in receiver clicks. In the arrangements of the invention the push-pull transmitter has its external electrodes directly connected in the line and has its central electrode grounded. This will result in a material saving in equipment and does away with transformers and other windings heretofore utilized. The elimination of such equipment will tend to reduce transmission losses. Other features and advantages of the invention will appear more fully from the detailed description thereof hereinafter given.

The invention may be more fully understood from the following description together with the accompanying drawing in the figure .coil 21.

of which is shown a circuit diagram embodying a preferred form of the invention.

In the circuit diagram are shown two subseribers stations A and B interconnected by a cord circuit L. The station at A comprises a loop circuit 1 having tip and ring conductors connecting the contacts of the jack at a central ofiice with the external electrodes of a push-pull transmitter 3. .The middle electrode of the transmitter 3 is connected to a retardation-coil 8 and thence to the con tacts' of switehhook 7 to ground. A bell 5 is also connected from the ring conductor of loop 1 to ground by the switchhook7. A line relay 6 is shown connected to the tip and ring conductors of the loop. A double winding receiver relay 1 is provided at station A having a winding inthe tip conductor and a winding in; the ring conductor of loop 1. At the central oflice is provided a cord circuit L which includes a repeating coil 21. There is also provided a supervisory relay 9 connected as shown. A grounded battery is connected to the midpoint of the windings of the repeating The apparatus at station B and the portion of cord L associated therewith is similar to thatheretofore described and no further description thereof will be given.

As maybe seen from the drawing, the supervisory or signaling path is obtained from the grounded battery 20, through the winding of supervisory relay 9, over the tip and, ring conductors of both cord and loop circuits in parallel to ground over the central electrode of transmitter 3 and contact of switch 7. The alternating talking currents generated by the transmitter 3 will serially traverse a complete metallic circuit comprising the tip conductors of loop land cord L, windings of repeating coil 21, and ring conductors of cord L and loop 1. Accordingly,

it will be seen that the talkingand supervisory paths are distinct and separate. The two windings of the receiver relay in the loop 1 are arranged so that the fluxes therein due to the supervisory currents oppose, whereas the fluxes therein due to the talking currents aid. Accordingly, the supervisory currents will not affect the receiver relay. It is pointed out that the function of the retardation coil 8 is to eliminate interfering noise which may be picked up from other circuits by an unbalance in the circuit shown on the attached diagram.

It is pointed out that While the subscribers ringer 5 has been shown as placed so as to be actuated by ringing current sent out over one side of the line to ground, nevertheless any number of other methods of supplying the subscriber with ringing current might equally Well have been employed. It is pointed out furthermore that while the talking battery .20 has been illustrated, as connected to the line through a repeating coil, nevertheless, in accordance with the principles of the invention, as heretofore set forth, the battery supply may be applied to the line through other agencies, such as retardation coils or bridged impedances.

Accordingly, while the invention has been disclosed as embodied in certain specific arrangements which have been deemed desirable, it is understood that it is capable of embodiment in many and other Widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. A transmission line comprising a cord circuit and a subscribers loop circuit, a push- -pull transmitter having its external electrodes directly connected to said loop circuit, a source of battery supply, means to apply current from said source in parallel over the tip and ring conductors'of said cord and loop circuits through said transmitter tofground, and supervisory means and receiving means included in said cord and loop circuits respectively.

2. A transmission line comprising a cord circuit and a subscribers loop circuit, a pushpull transmitter having its external eleotrodes directly connected to said loop circuit,

switching means for grounding the central electrode of said transmitter, a repeating coil in said cord circuit, and a grounded source of battery supply connected to the midpoints of the windings of said repeating coil. r 3. A transmission line comprising a cord circuit and a subscribers loop circuit, a pushpull transmitter having its external electrodes directly connected to said loop'circuit, means for applying a potential in parallel to the tip and ring conductors of said cord and loop circuits sequentially and through said transmitter to ground, and supervisory means in said cord circuit controlled by sai application of potential.

4. A transmission line comprising a cord circuit and a subscribers loop circuit, a pushpull transmitter having its external electrodes directly connected to said loop circuit, switching means for grounding the central electrode of said transmitter, a grounded source of battery supply in said cord circuit, means to apply currents from said source in parallel over the tip and ring conductors of said cord and loop circuits to ground through said transmitter, and a double Winding receiver relay having a Winding included in the tip conductor and a Winding included in the ring conductor of said loopcircuit, said windings being so arranged that the fluxes due to the currents transmitted in parallel over said tip and ring conductors will oppose each other. p I

In testimony whereof, I have signed my name to this specification this 13th day of December, 1927.

HENRY LADNER. 

